In display panels, a typical pixel design involves that three sub-pixels (including a red sub-pixel, a green sub-pixel and a blue sub-pixel) or four sub-pixels (a red sub-pixel, a green sub-pixel, a blue sub-pixel and a white sub-pixel) constitute one pixel (group) for display.
As user's demands on the feeling of watching a display screen improve (namely, a higher visual resolution is required, i.e., a display effect of higher resolution is achieved with relatively fewer physical pixels), it is necessary to increase the PPI (pixel per inch) of a display panel accordingly.